Amyloidosis is a clinical disorder caused by extracellular and/or intracellular deposition of insoluble abnormal amyloid fibrils that alter the normal function of tissues; AL amyloidosis results from extra-cellular deposition of fibril-forming monoclonal immunoglobulin light chains
Aetiology
AL amyloidosis is the most common type of systemic amyloidosis in developed countries (although still relatively rare)
The cause of amyloid production and its deposition in tissues is unknown
The average age of diagnosed patients is 65 years and fewer than 10% of patients are under 50
Pathophysiology
Plasma cell dyscrasia, related to multiple myeloma, in which clonal plasma cells in the bone marrow produce immunoglobulins that are amyloidogenic
This may be the outcome of destabilization of light chains owing to substitution of particular beta pleated sheet
Accumulation causes organ damage
Different protein to SAA amyloidosis (chronic inflammation) and familial amyloidosis
The clinical presentation is very varied because of the wide number of tissues or organs that may be affected
The most common presenting symptoms are weakness and dyspnoea
Renal manifestations are the most frequent, affecting two thirds of patients at presentation, with heavy proteinuria, nephrotic syndrome and impaired renal function in half of the patients
Clinical presentation
Heart involvement is present at diagnosis in more than 50% of patients and leads to restrictive cardiomyopathy
Investigations
Organ biopsy confirming AL amyloid deposition
Congo red stain - ‘apple-green’ birefringence under polarised light
Rectal or fat biopsy may be done if high clinical suspicion (less invasive)
Evidence of deposition of other organs
‘SAP’ scan
Echocardiogram/cardiac MRI
Nephrotic range proteinuria
Management
Treatment of AL amyloidosis is based on chemotherapy (similar to myeloma)
The presence and severity of amyloid heart disease is the main adverse prognostic factor
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